Effect Of Topography On Ground Motion Parameters

In this thesis, effect of topography on ground motion parameters is conducted thoroughly by creating different landform models and the measured hill in Wenxian, Gansu. To better understand this research, the situation of the site effect is reviewed briefly; the methods and the latest developments are summarized. The fundamental purpose is to reveal the reasons of damages increased on top of the irregular topography by studying the effect of topography on ground motion parameters in the3-D models, and to provide the basis for aseismatic design in hilly area affected by earthquake. Main contents and conclusions are as follows:(1) Collection of historical earthquake damages and strong seismic records. According to the information collected, statistics of the relationship between seismic damages and topographic features, suggest that the damages may increase on top of the irregular topography. Since topography is one of the important factors for researching the characteristics of ground motion, we should pay more attention to it.(2)3-D models of different landforms classified by geometric elements. There are six types of the sites:free space, valley shape, terraces shape, mountain ridge shape, tableland shape and bason shape. In order to reveal the rule of ground motion on various landforms, we input a single-frequency pulse to all the six3-D models. The result is that amplification of ground motion relate to the frequency of narrow band; the ratio of FFT spectra is of the significantly influenced by the incident frequency and geometric factors.(3) Analysis of the seismic effect on measured hill in Wenxian. A3-D model is created based on topographic survey, seismic exploration and soil sample test and so on. The strong motion records obtained aftershocks of the main Wenchuan shock are input. The result of the calculations is close to the observations, especially for the amplification ratio of the peak ground acceleration and the spectral ratio of the response spectrum, the most obvious amplification frequency is at1-10Hz. (4) Secondary development of Geological Modeling by FISH (programming language) in the commercial software FLAC. The computational efficiency and reliability of various models are compared from upper to lower in FLAC.